Our studies during the past year have been directed toward defining humoral immune changes following thermal injury, the efficacy of various biologic membranes available for post burn care, and the occurrence of immunosuppressive serum proteins following thermal injury. 1. Humoral immune function. We have studied the concentrations of serum IgA, IgG, IgM, C'3 and alpha 2M in 40 patients representing all grades of burn severity. In general, serum protein perturbations increase with the severity of the injury, immunoglobulins are generally depressed for the first week following injury then recover to normal or supra-normal levels, alpha 2M levels are depressed immediately following injury and remain depressed throughout the study period, and C'3 increases shortly after injury and remains elevated. 2. Biologic membranes. We conclude from our studies to date that fresh allograft (always included as a control membrane) is most effective for wound closure and is most effective at controlling wound bacteriology. Chorioamnion and frozen allograft are adequate, but less effective as biologic membranes. Least effective is procine skin, which however, is useful for short term applications. 3. Immunosuppressive serum proteins. We have found that spontaneous immune suppression is very common among burn patients, that suppression is profound, and is confined to cellular immune function. By manipulation of lymphocyte subpopulation we have determined that suppression effects are exerted through the generation of suppressor T-cells.